1. Field of the Invention
The present invention relates to a complete close-contact type image sensor for use in a small-sized facsimile or the like which reads an original without reduction in size.
2. Description of the Prior Art
Close-contact type image sensors can read originals without using an optical reduction system, so the optical path length is short and the device size can be reduced. Recently, therefore, they have been widely used as readers in small-sized facsimiles and bar code readers.
Among the conventional close-contact type image sensors there are those which employ an optical actual size system typified by selfoc lens in place of an optical reduction system to form an image on sensor elements.
Also, there has been developed a close-contact type image sensor of the type in which selfoc lens is not used in order to reduce the cost of the image sensor, and sensor elements are brought into close contact with an original to read an image. The close-contact type image sensor of this type will hereinafter be referred to as a complete close-contact type image sensor or merely as a sensor.
FIG. 6 is a schematic sectional view showing the structure of a conventional complete close-contact type image sensor. This sensor includes a glass substrate 86 on which there are formed a sensor element 2 coated with a protective film 82 and a contact portion 84 for the input and output of the sensor element 2; a printed circuit board 88 on which is placed the glass substrate 86 and which is provided with a driving IC 4 for taking out an electric signal stored in the sensor element 2; a thermo-pressure bonding electroconductive seal 90 which connects the contact portion 84 and the driving IC 4 with each other; a holder 92 which holds the printed circuit board 88, etc. therein; and a light source 94. The printed circuit board 88 is formed with a slit 96 for the transmission of light emitted from the light source 94. The numeral 6 denotes a roller which pushes an original 10 against the sensor element 2. The sensor element 2 is provided in a large number in the direction perpendicular to the paper surface according to the width of the original 10 to be read. The sensor having the construction just described above is disclosed in Japanese Patent Application No. Hei 02-305064.
The light emitted from the light source 94 passes through the slit 96 and is reflected by the original 10 and applied to the sensor element 2, whereby it is photoelectro-converted into an electric signal. The driving IC 4 drives the sensor element 2 through the contact portion 84 for input and output and also through the thermo-pressure bonding electroconductive seal 90, and reads information stored in the sensor element 2.
In the conventional sensor, at the time of reading information from the original 10, it is impossible to feed the original 10 in a stable manner because the path of transfer of the original 10 includes such bent portions 85 as shown in FIG. 6, thus often resulting in the occurrence of jam or deterioration of the image quality. In this case, the path of transfer of the original 10 can be made rectilinear by thickening the protective film 82. However, if the protective film 82 is made thick, there arises the problem that the gap between the original 10 and the sensor element 2 becomes larger and so the MTF (Modulation Transfer Function) is deteriorated.
In the complete close-contact type image sensor, moreover, since the sensor is pushed against the original by the roller 6 or the like, there arises the problem of abrasion of the sensor. In the conventional complete close-contact type image sensor, however, there is the drawback that the abrasion proceeds rapidly because it is only the protective film 82, such as a polyimide film as shown in FIG. 6, that is provided for the protection of the sensor element 2.
Further, in the conventional complete close-contact type image sensor, since the sensor is pushed against the original 10, there is generated static electricity by the sliding contact of the sensor with the original 10, which sometimes causes breakage of the sensor element 2.
The present invention has been accomplished in view of the above circumstances and it is an object thereof to provide a complete close-contact type image sensor capable of feeding an original stably without deterioration of MTF.
It is another object of the present invention to provide a complete close-contact type image sensor capable of improving the abrasion resistance.
It is a further object of the present invention to provide a complete close-contact type image sensor capable of preventing the breakage of sensor elements caused by static electricity.